Conversion of heavy oils by means of hot pebbles along a spiral path



Dec. 13, 1955 1.. c. BEARER ET AL 2,726,996 CONVERSION OF HEAVY OILS BYMEANS OF HOT PEBBLES ALONG A SPIRAL PATH Filed April 28 1950 2Sheets-Sheet l FIG. 5. INVENTORS.

L.C. BEARER R. R. GOINS BYWMW ATTORNE KS Dec- 3, 1955 L. c. BEARER ET AL2,726,996

CONVERSION OF HEAVY OILS BY MEANS OF HOT PEBBLES ALONG A SPIRAL PATHFiled April 28 1950 2 Sheets-Sheet 2 STEAM TO PRODUCT 75 RECOVERY 62 5 I5 OIL 6 i 6 OIL ELEVATOR PRODUCT TO QUENCH AND SEPARATION ZONE FIG. 6.

INVENTORS. L. C. BEARER R. R GOINS ATTORNEYS United States Patent huhCONVERSION OF HEAVY GIL-S BY MEAN S OF HGT PEBBLES ALQNG A SPIRAL PATHLouis C. Bearer Robert E. Gains, Bartlesville, Okia, assignors toPhillips Petroleum Company, a corporation of Delaware Application April2S, 3350, Serial No. 158,716

8 Claims. (Cl. 196-55) This invention relates to the conversion ofresiduum oil stocks. In one embodiment this invention relates to processand apparatus for the utilization of a contiguous movingmass ofparticulate solids in cracking heavy hydrocarbon oils.

Hydrocarbon oil residuum stocks are by-product heavy residual or bottomsfractions, obtained from distillation of crude petroleum, or resultingfrom certain refining operations. When any further treatment of thesestocks is attempted, such as distillation, or cracking, or the like,

excessive decomposition of the heavy material to carbon or heavycarbon-rich materials generally occurs, resulting in a rapidaccumulation of carbonaceous deposits and necessitating shut-down ofequipment after very short operating periods. Such short operatingperiods are uneconomical fro: l the standpoint not only of the cost ofshutting down and subsequently starting up, but also with respect to thetime and manpower requirements for removing the carbonaceous depositsand for readying the equipment for start-up. Furthermore, any desirablecracking product obtained is often of low quality and has it is oftenreferred to, usually comprises a series of substanti'allyvertically-extending zones, often in vertical alignment with each other.Usually two such zones are employed and are connected by a relativelynarrow interconnecting zone, or throat. The top or upper zone iscommonly referred to as the pebble heating chambenand the lower zone asthe gas reaction or gas heating chamber. A combustion zone, or chamber,is positioned adjacent or in close proximity to the sides of the lowerportion of the heating chamber. Combustion gas from the combustionchamber is passed through the mass of pebbles in the pebble heatingchamber. A hot gas source other than a combustion chamber is sometimesemployed. A contiguous mass of particulate contact material, oftenreferred to as pebbles, fills the pebble heating zone, theinterconnecting zone or throat, and the gas reaction or heating zone,and flows downwardly through these zones by gravity. Pebbles aredischarged from the bottom of the gas reaction zone at a controlled rateand returned, usually by elevating means, to the inlet in the upperportion of the pebble heating zone. A contiguous moving pebble massthereby fills the pebble heating zone, gas heating zone, and theinterconnecting zone, or throat, at all times.

The term pebble as used throughout the specification denotes any solidrefractory material of fiowable form and size that can be utilized tocarry heat from one zone 2,726,996 Fat-tented. Dec. 13, 1955 to another.Pebbles are preferably substantially spherical and about inch to 1 inchin diameter, the preferred range being about inch to /2 inch. Pebblesare formed of a refractory material which will withstand tempera turesat least as high as the highest temperature attained in the pebbleheating chamber, and must be capable also of withstanding temperaturechanges within the apparatus. Refractory materials such as metal alloys,ceramics, or other satisfactory material may be utilized to form suchmaterials. Silicon carbide, alumina, periclase, thoria, beryllia,stellite, zirconia, and mullite may be satisfactorily used to form suchpebbles or may be used in admixture with each other or with othermaterials. Pebbles formed of such materials, when properly fired, servevery well at high temperatures. Some pebbles withstand temperatures upto about 3500 F. Pebbles which are used may be either inert orcatalytic, as used in any selected process.

Pebble heater apparatus is generally employed in the thermal treatmentor conversion of reactant materials, often hydrocarbons. Operation ofsuch a pebble system generally involves circulating a contiguous pebblemass through the pebble heating chamber, interconnecting throat andreaction charnber. That portion of the pebble mass descending throughthe heating chamber is heated to a suitable predetermined temperatureabove a desired treating or conversion temperature in heat exchangerelation with combustion gas or other hot gases from any desired source.Pebbles are often heated in the heating chamber to temperatures as highas from 2,000 to 3,000 F., and in some cases higher, dependent upon thetemperature requirements of the subsequent treating step. The thusheated pebbles passing through the reaction chamber are contacteddirectly with the material to be treated or converted for a suitablecontacting time to effect the desired treatment. The pebble mass havinggiven up heat to the material treated in the treating zone, descendsthrough the bottom of the reaction chamber and is fed to an elevator forfurther handling, generally for transfer to an inlet at the top of thepebble heating chamber for reheating and recirculation through thesystem.

In cracking oil residuum stocks in pebble heater apparatus in accordancewith conventional methods, a considerable amount of agglomeration ofpebbles with accumulated carbon and carbon-rich byproduct takes placeafter being on stream for only a short period with the result thatpebble circulation is impaired, and often stopped entirely. This occursparticularly at the higher cracking temperatures required, in manyinstances being as high as from 1,000 to 1,7G0 F.

In introducing an oil residuum feed into contact with a mass'of pebbles,great difliculty is experienced in uniformly contacting all the pebblesin the mass, so that each pebble'is coated with an equal amount of oil.Instead,

-. disproportionately large amounts of oil reach only a relatively smallportion of the hot pebble mass, with the result that large quantities offree flowing oil move through that small proportion of pebble masscontacted, while the remaining portion of the pebble mass passes throughthe system unutilized. Furthermore, considerable coking of the freeflowing oil to form carbonaceous lay-product takes place, thus reducingefficiency of the conversion to a level not economically feasible; andagglomeration of pebbles and carbonaceous by-product thus formed, takesplace. Such agglomeration of carbonaceous matter and pebbles is, ofcourse, undesirable since the pebble system must then be shut-down foran extended period for removal of the agglomerate and for readying theequipment for re-start-up.

Our invention, in a broad embodiment, is concerned with the utilizationof a contiguous moving mass of particulate solids in the treatment ofresidual oil stocks, particularly in a pebble heater system, underconditions preventing the agglomeration of the particulate contactingmaterials with carbonaceous by-product and providing for the conversionof the heavy charge material to valuable hydrocarbons, over periods oflong duration.

An object of this invention is to provide for the conversion ofhydrocarbons.

Another object is to provide an improved pebble heater apparatus.

Another object is to provide a process for utilizing a contiguous movingmass of particulate solids in the conversion of residual hydrocarbonstocks to lighter materials.

Another object is to provide an apparatus for uniformly coating all thesolid particles in a contiguous moving mass of particulate solids, withan oil.

Another object is to provide process and apparatus for cracking oilresiduum stocks in a pebble heater system, and for continuously removingfrom the system carbon and carbon-rich materials formed therein asby-products of the cracking.

Other objects will be apparent to those skilled in the art from theaccompanying discussion and disclosure.

In accordance with one embodiment of our invention, we provide processand apparatus for introducing a hydrocarbon oil residuum stock intocontact with pebbles in a pebble heater system in a manner such that allpebbles entering the conversion chamber have initially been uniformlycoated with oil feed. In this manner some of the lighter components maybe immediately vaporized upon contacting the hot pebbles, and suchvapors are immediately withdrawnyheavier oil components remaining on thehot pebble surfaces are converted as the pebble mass moves downwardlythrough the conversion chamber as a result of the increased residencetime in the pebble mass. Gaseous conversion products are withdrawn fromthe conversion chamber. As the pebble mass moves downwardly, the morerefractory feed components remaining on the pebble surface are graduallyconverted to desired product as a function of the prolonged residencetime. Finally, as pebbles approach the pebble discharge point in or nearthe bottom of the conversion chamber, the refractory carbonaceousby-product remaining on their surfaces is substantially dry as a resultof the reaction of substantially all reactive components on the pebblesurfaces to form conversion product. Pebbles carry the dry carbonaceousmatter from the conversion chamber adhered to their surfaces, and arerecycled to the heating chamber where they are reheated, burned free ofcarbonaceous matter, and recirculated.

The pebbles in the pebble mass are uniformly coated with the oil feed,by constricting the crosssectional dimension of the pebble stream at thepoint or points of contact of the oil and pebble mass, and by regulatingthe relative flow rates of pebbles and oil at those points. Thepebbleoil contacting is eifected prior to entry of pebbles into theconversion chamber proper. All pebbles entering the conversion chamberare uniformly coated with oil, and the amount of oil introduced islimited to that coating the pebbles, so that agglomeration of pebbleswith carbonaceous by-product, ordinarily taking place when there is freeflowing oil in the pebble mass, is avoided. In this manner agglomerationof pebbles and oil is prevented and free flow of the pebble mass ismaintained. Carbon or carbon-rich by-product materials thus formedadhere to the pebble surfaces, there being no other carbon containingby-product in the system. In this manner available surface area isprovided for converting the more refractory feed components to crackingproduct and for continuously removing the final carbon residue in a mostreduced form, from the conversion system.

Broadly, our invention provides for constricting the flow of acontiguous moving mass of particulate solids and introducing an oil feedstock in contact with the par- 4 ticulate solids from within thatportion of the moving mass, at arate dependent upon the rate of solidsflow and the cross-sectional dimension of the constricted moving solidsmass.

Our invention, in a preferred embodiment, provides for introducing theoil feed into contact with pebbles in a pebble heater apparatus, atpredetermined points within an interconnecting conduit or pebble throat,and for regulating the number of oil inlets with respect to thecrosssectional dimension of the pebble mass moving through the throat,and then regulating the oil charge rate in relation to the rate of flowof the pebble mass through the throat. We have found that when we pass astream of a contiguous mass of pebbles having a thickness orcrosssectional dimension not exceeding 30 pebble diameters into contactwith a single stream of hydrocarbon oil feed in a weight ratio ofpebbles to oil feed of at least 14:1, at temperatures required forcracking such oil stocks, generally from 800 to 1700 F., the pebbles inthe moving stream can be initially uniformly coated with oil and thatagglomeration of pebbles and carbonaceous by-product is prevented.Accordingly, after contacting pebbles with oil feed, as described above,some lighter components of the feed may immediately vaporize, in whichcase such vapors are withdrawn immediately. The remainingfeed componentsare gradually converted to lighter product, as a function of prolongedresidence time, as the pebbles pass downwardly through the conversionchamber, such product being withdrawn as formed. The conversion of thefeed components in the conversion chamber is more extensive than can beobtained when employing pebble heater apparatus in accordance withconventional cracking methods. Consequently, in addition to theadvantages discussed above, our invention provides for a more efficientprocess for cracking heavy oil residuum cracking stocks, both withrespect to the high yields of desired products, and to the concomitantlylower yields of undesirable carbonaceous by-products that are obtained.

The accompanying diagrammatic drawings illustrate preferred forms ofapparatus and process of our invention, and are discussed in terms ofconverting heavy hydrocarbons in a pebble heater system. It is to beunderstood however, that our invention is well applied also to theutilization of a contiguous moving mass of flowable solid particulateheat transfer materials of any type in converting oils, and that variousmodifications of the process and apparatus illustrated can be made andstill remain within the scope of our invention.

Figure l is an elevation in cross section of one embodiment of apparatusof our invention, providing for injection of oil feed into the pebblethroat of a pebble heater apparatus, at a plurality of points onto alayer of pebbles of regulated thickness passed downwardly over a conicalsurface, and then downwardly and away from the conical surface toprovide pebbles uniformly coated with oil feed at the inlet to theconversion chamber. Figure 2 is a cross-sectional elevation of anembodiment of apparatus illustrative of a fixed screw member axiallydisposed in a pebble throat of a pebble heater apparatus, providing forlimiting the thickness of a downwardly moving pebble layer and foruniformly contacting the pebbles with oil feed; Figure 3 is across-sectional elevation of an embodiment of apparatus of ourinvention, providing for passing the pebble stream through the pebblethroat along a zig-zag path defined by alternate down-' wardly extendingbaffle members positioned to limit the thickness of the pebble layer, asdiscussed, and for introducing oil feed into contact with the pebblelayer thus formed. Figure 4 is a plan view in cross section of anarrangement of apparatus providing for directly contact-'- the apparatusof Figure 4 taken along the line 55. Figure 6 is a cross-sectional viewof the apparatus of Figure '1 taken along the line 66. Figure 7 is acrosssectional view of the apparatus of Figure 3 taken along the line7-7. Figure '8 is a diagrammatic illustration of one manner in which theapparatus of our invention can be utilized in conjunction withconventional pebble heater apparatus, in the conversion of hydrocarbons.

Referring to Figure l, downwardly extending conduit 10 in communicationat its upper end with pebbles in a pebble heater apparatus (not shown)extends vertically into housing, or shell, 11, and terminates therein ata distance of at least 4 pebble diameters above cylindrical bafliemember 12 having an open bottom 13 and a perforate conical top 14, andaxially disposed with respect to conduit 10. Conduit 16 is axiallydisposed with respect 'to baffle 12, in the bottom member 17 of housingmember 11. Bottom member 17 is preferably conically shaped so that thecontour of its interior wall portion simulates a cone. Vapor outletconduits 18 are disposed in the top of housing 11. Oil inlet conduits 19extend into housing 11 and terminate in a downward direction therein, ata point above the lower end 21 of conduit 10. Oil inlet conduits 22extend into housing 31 and into cylindrical baffie member 12 andterminate therein in a downward direction, at points above open bottomend 13.

In the operation of the embodiment of Figure 1, the oil feed is injectedinto contact with flowing pebbles moving as a layer over conical surface14, and downwardly from surface 14 through annulus 23, describedhereafter. The thickness of the pebble layer on surface 14 preferablydoes not exceed 30 pebble diameters. The Width of annulus 23 is limitedto that at which no bridging of pebbles takes place, generally a minimumof about 4 pebble diameters. Operating in this manner, substantially allpebbles passed over surface 14 and on through annulus 23, are completelycoated with oil and no free flowing oil is present in the pebble mass.However, in some instances all of the oil may not immediately coat thepebbles, in which case the small amount of free moving oil willeventually cover them as a result of the intermixing or" oil and pebblesthat takes place. The annular space formed by baflie member 12 andhousing 11 is preferably of about the same dimension as the distancebetween conduit end portion 21 and the top of baffle member 12, so thatthe pebbles flowing from conduit 10 across the top of the conicalsurface 14 and on downwardly through annular space 23 and belowcylindrical baflle member 12 into conduit 16, are moving at a relativelyhigh rate to provide for uniformly contacting the oilwith the pebbles byvirtue of the mixing and intermingling of pebbles and oil that takesplace along this line of pebble flow. In order to prevent the presenceof excess free moving oil in the pebble mass as it passes downwardlythrough housing 11, the weight ratio of pebbles to oil introduced intocontact therewith is maintained at a value not lower than 14:1, suchratios-preferably being higher, often from about :1 to :1. Althoughhigher ratios can be employed in the practice of our invention, aportion of that flowing pebble mass would pass through the systemwithout being contacted with oil feed. The total oil introduced intocontact with pebbles, whether through all the conduits 19 and conduits22, or only some of these conduits, is the amount of oil referred to inthe weight ratio of pebbles to oil discussed above. In some instances itmay be advantageous to introduce all of the oil feed through conduits19, but in many instances uniform contact of oil with pebbles can moreeasily be achieved by employing conduits 22 in conjunction with conduits19, or through conduits 22 alone.

With reference to Figure 2, upright cylindrical conduit, or shell, 31,connected at its upper end with a pebble heating chamber and at itslower end with a reaction chamber of a pebble heater apparatus, containsstationary screw 32 axially disposed with respect to chamber 31 and ihaving a diameter less than that o'f'chamb'er 3'1,"but only by less thanone pebble diameter. The pitch of screw member '32 is such that pebblespassed on to the rib portions will continue to pass downwardly bygravity instead of forming a stationary pile, the pitch beingnecessarily above the angle of repose of the pebble mass, which angle isoften from about 28 to 35, dependent on the size and shape of thepebbles and the characteristics of their surfaces. A plurality of oilinlets 33 extend through the side wall of chamber 31 and terminate aboveseparate rib portions of screw member 32. The ribs of screw 32 "are;spaced apart a minimum distance of 4 pebble diameters and preferably notgreater than 30, so that bridging of pebbles will not occur and allpebbles will be initially coated with oil. As stated above, a layer ofpebbles hav-;

ing a thickness exceeding 30 pebble diameters can be employed, but undersuch conditions some pebbles may pass through the system Without beingcontacted with oil feed. In the operation of the embodiment of Figure 2the total amount of oil introduced through oil inlets 33 is.

regulated to conform with the total amount of pebbles passed throughchamber 31 to a value above the pebble to oil weight ratio discussedabove. In introducing oil in contact with pebbles passing along thespiral path as determined by screw member 32, a large amount of mixingand churning of pebbles takes place to absorb all the oil added, so thatpebbles leaving chamber 31 are all uni: formly coated with oil feed. Anyvapors formed in chamber 31 as a result of initial contact of oil withhot pebbles are withdrawn from chamber 31 through at least one of aplurality of conduits 34. Pebbles leaving chamber "31. are uniformlycoated with oil feed and are introduced into a reaction chamber of apebble heater apparatus (not shown). 7

Referring to Figure 3, upright elongated conduit, or shell, 41 isconnected at its upper end with a pebble heat ing chamber and at itslower end with a reaction chamber of a pebble heater apparatus (notshown). 'Bafile' members 42 comprise a series of battles alternatelydisposed along the length of chamber 41 so as to slope laterally anddownwardly from opposite sides thereof, the

lower end 43 of each baffle being spaced from the wall ofchamber 41 aminimum distance of 4 pebble diameters and being spaced above the otheralso at a minimum dis-' tance of 4 pebble diameters, and preferably notmore than 30 pebble diameters, for the same reason discussed above.

minate at a point within the chamber, preferably in a downwarddirection, each above a separate bafile member 42.

In the operation of the embodiment of Figure 3, hot pebbles from thepebble heating chamber are passed first. onto the topmost bafiie member42, then from theend 43 thereof onto the next bafile member andcontinuously along a zig-zag path through chamber 41. The pebblesmovingon each of the bafile members are contacted with fresh oil feed, and theratio of total pebbles to' total oil introduced into chamber 41 ismaintained above the minimum weight ratio of 14:1, discussed above. Inthis man-- ner, pebbles moving along the bafiie members throughcontacting hot pebbles in chamber 41, and are removed through one ormore of conduits 44.

Referring to Figure 4, a cylindrical upright conduit, or

shell, 51 is connected at its upper end with a pebble heating chamberand at its lower end with a conversion cham ber of a pebble heaterapparatus (not shown). Oil'inlets 52 extend through the side wall ofchamber51'an'd are disposed to terminate at points within the mass ofpebbles 3 Vapor outlet conduits 44 extend from within chamber 41 to anoutside point, at points directly under the upper end of each bafflemember. Oil inlet conduits: 46 extend through the side wall of chamber41 and ter-.

7 passing through chamber 51. A preferred arrangement of oil inletconduits 52 is further illustrated with respect to the cross-sectionalelevation of Figure 5, taken along the line 5 of Figure 4. i

Operating in accordance with the embodiment of Fig ure 4, the Weightratio of total pebbles passed through chamber 51 to oil introduced intocontact therewith is maintained above the minimum ratio of 14:1,discussed hereabove, and by disposing oil inlets 52 to terminate Withinthe pebble mass passing through chamber 51 at predetermined selectedpoints pebbles are uniformly contacted with oil feed, and no freeflowing oil is present in the pebble mass leaving chamber 51.

Figures 6 and 7 further illustrate the arrangement of apparatus in eachof Figures 1 and 3 respectively, Figure 6 representing a cross-sectionalview of Figure 1 taken along the line 6-6, and Figure 7 representing acrosssectional view of the apparatus of Figure 3 taken along the line77.

With reference to Figure 8, operation of a pebble heater system inconjunction with apparatus and process of our invention isdiagrammatically illustrated. In the operation of the pebble heaterapparatus of Figure 8, a contiguous moving mass of pebbles is circulatedthrough pebble heater chamber 61, pebble throat 60, and conversionchamber 63, pebbles being withdrawn from chamber 63 through conduit 64and introduced into elevating means 66 for recycle through line 67 tothe heating chamber. Pebble flow through the pebble heater system isregulated by means of star valve 70, or other suitable means well knownin the art. Pebbles introduced into pebble heating chamber are passeddownwardly in contact with upwardly flowing hot heat transfer gasesintroduced through line 68. Optionally, gases introduced into chamber 61through line 68 may comprise components of a combustible fuel gasmixture which is then burned on the pebble surfaces in chamber 61, orburned in a separate combustion chamber immediately subjacent chamber 61(not shown) to form hot combustion gases, which are then passed upwardlyin contact with pebbles in chamber 61. In either case, pebbles passingdownwardly through chamber 61 are heated in heat transfer relation withhot gases, to a level above'a predetermined conversion temperaturerequired in chamber 63, discussed hereafter. Heat transfer gases, havingimparted heat to pebbles in chamber 61, are discharged through line 69.

62, disposed in throat 60, comprising an apparatus of our invention suchas illustrated in Figures 1, 2, 3, or 4, and further illustrated inFigures 5, 6, and 7. Throat 60 can be considered as comprising oil-feedcontacting zone 62, with line 60 providing for conducting flow ofpebbles into zone 62, and from zone 62, as illustrated in Figure 8. Oilis introduced into contact with pebbles in zone 62 through lines 65 in atotal overall weight ratio of pebbles to oil above the minimum of 14:1.Pebbles and oil are intermingled in zone 62 in a manner describedhereabove such that no free moving oil is present in the pebble massdischarged from throat 60 through zone 62, into conversion chamber 63.Upon contacting oil with pebbles in zone 62, some vapors immediatelyform and are withdrawn from zone 62 through line 75. Pebbles passingfrom throat 60 into conversion chamber 63 are coated uniformly with thetotal oil feed, except for any vaporization of lighter feed componentsthat may take place upon initial contact of oil and pebbles. Thetemperature of pebbles moving through chamber 63 is controlled by theheating step in chamber 61, wherein the pebbles are heated to atemperature sufiiciently high to compensate for pebble heat losses thatoccur between zone 61 andzone 63, and to provide for introduction ofpebbles into chamber 63 at a requisite conversion temperature. Generallythe temperature of oil-pebbles entering chamber 63 will be within thelimits of about 800 to 1700 F. As pebbles pass downwardly throughchamber 63, the less refractory components of oil feed on the pebblesurfaces are the first to react to form cracking product. As the pebblescontinue downwardly through chamber 63 the more refractory componentsreact to form cracking product as a function of the extended residencetime, until pebbles approaching the lower end of chamber 63 contain onlythe most refractory oil components, most of which are finally reactedand remain as dry carbonaceous residue on the pebble surfaces. Pebblesdischarged from chamber 63 through line 64 carry with them the residualcarbonaceous by product in a dry form. Pebbles leaving line 64 areelevated to conduit 67 and returned therethrough into chamber 61, wherethey are reheated and burned free of carbonaceous matter, the burningbeing supported by the introduction of excess oxygen for that purposethrough line 68.

Operating in accordance with the apparatus and process discussed withreference to Figure 8, there is substantially no free flowing liquid inthe pebble mass, thereby preventing undue carbonization of masses of oilfeed to form large pieces or chunks which would then agglomerate withpebbles to form large slow moving or stationary masses, and ultimatelystop pebble flow entirely. In accordance with our invention asillustrated in Figure 8, the amount of oil with respect to pebbles, isregulated, and the intermixing of pebbles and oil is efiected in amanner so that pebbles are uniformly coated with the oil, and any carbonby-product remains on the pebble surface as residue and is continuouslyremoved with the pebbles, from the conversion chamber.

Advantages of this invention are illustrated by the following example.The reactants and their proportions and other specific ingredients arepresented as being typical and should not be construed to limit theinvention unduly.

A heavy hydrocarbon oil residuum having an API gravity of 16, is chargedinto the interconnecting throatof a pebble heater apparatus having athroat diameter of 4 inches, at a'rate of 71 pounds per hour. Pebblesare circulated through the unit at a rate of 1850 pounds per hour, andseal steam is introduced into the bottom of the reaction chamber at 65pounds per hour and into the top of the pebble throat at 20 pounds perhour. Efiluent gases and vapors are withdrawn from the space above thereactor pebble bed at a temperature of 1140 F. and are immediatelyquenched. Pebbles enter the reaction chamber at a temperature of 1180 F.

On the basis of the weight of oil feed, gaseous and liquid crackingproducts obtained amount to 91 per cent, 36% being recovered as gaseousproduct. The remaining 9 per cent is carbon, which is removedcontinuously from the system on the surfaces of pebbles withdrawn fromthe reaction chamber. No agglomeration of carbonaceous by-product withpebbles takes place. The total gaseous product has the followingcomposition:

The following distillation and gravity characteristics Mol .percent' 9further identify the charge stock employed and the liquid crackingproduct obtained.

4. The process of claim 3 wherein a plurality of streams of oil feed areintroduced into said contacting zone in Original Feed Gasoline ght GasHeavy Gas ASTM Distillation, F rap-400 011, 490 on, rgo 5 9 193 VacuumFlash F. F.-750 F. F.900 F Evaporated .l 985 990 224 496 30 Cracked 1,075 282 570 End Point-- 409 Rev 98. 0 930 Res 1. 0 6. 1

API Gravity, at 60 F 16.0 38.0 20.4

Sp. G. 79 F .l

As will be evident to those skilled in the art, various modificationscan be made or followed, in the light of the foregoing disclosure anddiscussion, without departing from the spirit or scope of the disclosureor from the scope of the claims.

We claim:

1. A process for cracking a hydrocarbon oil residuum by contacting samein heat exchange relation with pebbles, comprising heating a mass ofpebbles to a temperature above a predetermined requisite temperature forcracking said residuum, gravitationally passing pebbles thus heateddownwardly through an initial oil-pebble contacting zone along a spiralpath as a layer having a depth of from 4 to 30 pebble diameters,introducing a plurality of streams of liquid oil residuum into directcontact with hot pebbles at points from within said contacting zonedisposed along said spiral path in a weight ratio of total pebbles tototal oil thus contacted of from 14:1 to 30:1, removing vapor from saidoil-pebble contacting zone at a plurality of points along said spiralpath of pebbles, passing resulting hot oil-coated pebbles from saidinitial contacting zone to an oil cracking zone at said predeterminedcracking temperature under time conditions to crack oil coated on saidpebbles, and recovering vaporous oil cracking product from said crackingzone as a product of the process.

2. The process of claim 1 wherein pebbles are withdrawn from saidcracking zone containing carbon on their surfaces and are recycled tosaid heating and burned free of carbon prior to being passed to saidoil-contacting zone.

3. In a process for cracking a liquid hydrocarbon oil in heat exchangewith hot pebbles, the improvement comprising passing a stream ofpebbles, heated to a temperature at least as high as that required insaid heat exchange, along a spiral path through an oil'pebble contactingzone, introducing at least one stream of liquid oil feed onto surfacesof pebbles in said contacting zone, coating pebbles with a film of saidliquid oil feed in said contacting zone by maintaining pebble streamthickness therein of at least 4 pebble diameters and passing pebbles andoil into said contacting zone in a pebble to oil weight ratio of atleast 14:1, thereby preventing undue carbonization of oil withconcomitant agglomeration of pebbles and carbonaceous materials andimpairment of pebble flow.

spaced apart relationship.

5. The process of claim 4 wherein a portion of hydrocarbon feed isvaporized in said contacting zone and wherein vapors are immediatelywithdrawn from said zone at a plurality of points each in spacedrelation with points at which feed is introduced into said zone.

6. In a process for cracking a hydrocarbon oil residuum upon contactingsame with hot pebbles, wherein the pebbles are first heated in a pebbleheating zone to pro vide a cracking temperature when contacted with saidoil residuum as described hereinafter, and then gravitated to a reactionzone through a throat inter-connecting said heating and reaction zones,and in said reaction zone contacting said oil residuum with said pebblesat said cracking temperature, the improvement comprising passing astream of pebbles having a thickness of at least 4 pebble diameters,from said heating zone, along a spiral path through saidinter-connecting throat, introducing at least one stream of said oilresiduum onto surfaces of pebbles in said throat in a weight ratio oftotal pebbles to total oil of at least 14:1, thereby preventing unduecarbonization of oil with concomitant agglomeration of pebbles andcarbonaceous materials and impairment of pebble flow.

7. The improvement of claim 6 wherein said thickness of pebbles is inthe range of 430 pebble diameters and said weight ratio is in the rangeof 14:1 to 30:1.

8. The improvement of claim 7 wherein said weight ratio is at least20:1.

References Cited in the tile of this patent UNITED STATES PATENTS1,702,738 Manley Feb. 19, 1929 1,976,000 Apgar et al. Oct. 9, 19342,338,573 Creelman Ian. 4, 1944 2,362,621 Fahnestock Nov. 14, 19442,389,399 Alther Nov. 20, 1945 2,438,261 Utterback Mar. 23, 19482,444,128 Anderson June 29, 1948 2,448,334 Watson Aug. 31, 19482,534,752 Beckberger Dec. 19, 1950 2,614,824 Weber Oct. 21, 1952

1. A PROCESS FOR CRACKING A HYDROCARBON OIL RESIDUUM BY CONTACTING SAMEIN HEAT EXCHANGE RELATION WITH PEBBLES, COMPRISING HEATING A MASS OFPEBBLES TO A TMEPERATURE ABOVE A PREDETERMINED REQUISITE TEMPERATURE FORCRACKING SAID RESIDUUM, GRAVITATIONALLY PASSING PEBBLES THUS HEATEDDOWNWARDLY THROUGH AN INITIAL OIL-PEBBLE CONTACTING ZONE ALONG A SPIRALPATH AS A LAYER HAVING A DEPTH OF FROM 4 TO 30 PEBBLE DIAMETERS,INTRODUCING A PLURALITY OF STREAMS OF LIQUID OIL RESIDUUM INTO A DIRECTCONTACT WITH HOT PEBBLES AT POINTS FROM WITHIN SAID CONTACTING ZONEDISPOSED ALONG SAID SPIRAL PATH IN A WEIGHT RATIO OF TOTAL PEBBLES TOTOTAL OIL THUS CONTACTED OF FROM 14:1 TO 30:1, REMOVING VAPOR FROM SAIDOIL-PEBBLE CONTACTING ZONE AT A PLURALITY OF POINTS ALONG SAID SPIRALPATH OF PEBBLES, PASSING RESULTING HOT-COATED PEBBLES FROM SAID INITIALCONTACTING ZONE TO AN OIL CRACKING ZONE AT SAID PREDETERMINED CRACKINGTEMPERATURE UNDER TIME CONDITIONS TO CRACK OIL COATED ON SAID PEBBLES,AND RECOVERING VAPOROUS OIL CRACKING PRODUCT FROM SAID CRACKING ZONE ASA PRODUCT OF THE PROCESS.